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ALib C++ Library
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This type is used as the default class to provide access to program data when evaluating ALib expressions. Usually a derived type which contains references to necessary application data is passed to method Expression::Evaluate . Then, custom callback functions may cast this object back to its original type and access such application data.
Also, scope objects are used to store intermediate results and of-course the final one, in the case that such results are not of a simple type that can be boxed Box "by value".
For this, different simple allocator objects are provided. A custom, derived type may add own storage facilities, for example vectors of custom objects which are deleted when the vector is deleted.
A scope object can be reused for evaluating the same expression several times. Prior to evaluation, the custom "scoped data" has to be set. With each reuse, method Reset will be invoked internally. Hence, if custom 'allocators' are added in derived types, this method has to be overwritten to a) invoke the original method and b) clean such custom types.
One singleton of this type, used to store compile-time data is created with virtual method Compiler::getCompileTimeScope . If compile-time invokable custom callback methods use custom storage allocators, this method has to be overridden to return the proper custom version of this class. (Note, this is not needed for the evaluation-time instances, as this is created in the custom code unit anyhow and passed to method Expression::Evaluate .
#include <scope.hpp>
Public Field Index: | |
| MonoAllocator | Allocator |
| Scope * | CTScope |
| SPFormatter | Formatter |
| HashMap< NString, ScopeResource * > | NamedResources |
| std::vector< Expression *, StdContMA< Expression * > > | NestedExpressions |
| std::vector< ScopeResource *, StdContMA< ScopeResource * > > | Resources |
| std::vector< alib::Box > | Stack |
Public Method Index: | |
| ALIB_API | Scope (SPFormatter &formatter) |
| virtual | ~Scope () |
| bool | IsCompileTime () |
| virtual ALIB_API void | Reset () |
| MonoAllocator Allocator |
Block-allocator used to store temporary data and results. The allocated data within this object becomes cleared automatically by method Reset, in the moment an expression is evaluated a next time (usually with different custom scope data).
Note that this allocator is not cleared for the compile-time scope object CTScope.
| Scope* CTScope |
This is a pointer to the compile-time scope. This is available only at evaluation time and primarily is used to access field NamedResources. This allows to create resources at compile-time, which can be used for evaluation.
A sample use case is implemented with built-in compiler plug-in Strings . When wildcard or regex matching is performed on constant pattern strings, the matching class (which itself "compiles" the pattern once) is created once and reused during evaluation.
Used to convert numbers to strings and vice versa. In addition expression function Format of built-in compiler plugin Strings uses this object to perform the formatting of arbitrary objects according to a given format string.
Hence, to support customized format strings, a different formatter is to be passed here. Default format string conventions provided with ALib are python style and java/printf-like style .
The default implementation of method Compiler::getCompileTimeScope provides field Compiler::CfgFormatter with the constructor of the default compile-time scope.
| HashMap<NString, ScopeResource*> NamedResources |
| std::vector<Expression*, StdContMA<Expression*> > NestedExpressions |
| std::vector<ScopeResource*,StdContMA<ScopeResource*> > Resources |
| std::vector<alib::Box> Stack |
This is the argument stack used by class detail::VirtualMachine when evaluating expressions.
| Scope | ( | SPFormatter & | formatter | ) |
Constructor.
Usually, for parameter formatter field Compiler::CfgFormatter should be provided.
| formatter | A reference to a std::shared_ptr holding a formatter. Usually Compiler::CfgFormatter . |
Definition at line 54 of file compiler.cpp.
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This function may be called (respectively provides reliable results) only from within callback functions that this scope is passed to.
true if this is a compile-time invocation, false otherwise.
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virtual |
Scope objects usually are reused, either for evaluating the same expression using different scoped data (attached to derived versions of this class), or for evaluating different expression.
Such reuse is internally detected and if so, this method is invoked.
Instances of this class used as compilation scope, are not reset during the life-cycle of an expression.
Derived versions of this class need to free allocations performed by callback functions.
Definition at line 67 of file compiler.cpp.